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Jeremy Rehm

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Most of the sea ice that forms in the Arctic is thinner than it's been in decades.Credit: Kathryn Hansen/NASA

The Arctic experienced its second-warmest year on record between October 2017 and September 2018, according to the annual Arctic Report Card. And average air temperatures in this frigid region have hit record or near-record levels every year since 2014.

Temperatures in the Arctic are now increasing at roughly twice the rate of the global average, researchers say in the report released by the US National Oceanic and Atmospheric Administration (NOAA).

Warming is causing changes across the entire Arctic, and those changes are building, said Emily Osborne, the programme manager at the NOAA Arctic Research Program in Silver Spring, Maryland. She helped to present results from the report on 11 December during a meeting of the American Geophysical Union in Washington DC.

Wild reindeer and caribou populations, for example, have declined by more than 50% since the 1990s. And more than 99% of sea ice is now considered relatively new, meaning that it hasn’t lasted for more than four summers without melting. It’s now the thinnest and most susceptible to warming temperatures that it's been in 30 years.

Harmful algal blooms are seven times more prevalent off the Alaskan coast than they were 40 years ago. And the Arctic Ocean now contains the highest concentration of microplastics of any ocean basin in the world, according to the report.

The microplastics and algal bloom findings really surprised Donald Perovich, a geophysicist at Dartmouth College in Hanover, New Hampshire, who worked on the report card. “Even here — the farthest point on Earth— we’re still seeing impacts from lower latitudes,” he says.

doi: 10.1038/d41586-018-07733-y

Updates & Corrections

Update 11 December 2018: This story has been updated with information on harmful algal blooms and microplastics in the Arctic, as well as comments from Emily Osborne and Donald Perovich.